The present invention relates to an electric throttle-control apparatus and a motor used in the apparatus.
In a conventional throttle system used in a car, since the throttle system is mechanically composed such that the throttle valve is opened and closed according to the operation of an acceleration pedal via a wire, the quantity of the pedal-operation directly corresponds to the open degree of the throttle valve. Recently, a highly accurate control of a throttle valve has been required from the view points of the regulations to exhaust gas, and improvements for fuel consumption, safety, and salability, and the electrical throttle-control system (hereafter referred to as an ETC system).
As shown in FIG. 26, National Publication of Japanese-translated version Hei-500677 (WO88/02064) discloses an apparatus for electrically controlling intake air flowing into an internal combustion engine: the apparatus including an intake air flow path 10, a throttle valve 11 fixed to a rotatably set shaft 12 located in the intake air flow path 10, and a first return spring 15, which is always engaged with the shaft 12, for applying a torque in the direction of closing the throttle valve 11. Further, the throttle valve 11 is guided by the return spring 15 to the stop position of the minimum open angle xcex1r ( greater than 0) toward the stopper to which a spring-load is applied by an opposing spring 21. In addition, a rotation-adjusting unit 13, in which a motor is used, is controlled so as to generate torque, corresponding to torque to open the throttle valve 11 to the maximum open angle.
Also, as shown in FIG. 27, Japanese Patent Publication Hei 7-72503 discloses a load-adjusting apparatus including a control element 11 connected to a transmission member 4 further connected to an acceleration pedal 1, which acts on a throttle valve 16 in an internal combustion engine, and on the electrical servo-driving unit 9 along with a target operation amount-detection element 7 attached to the transmission element 4. Further, the control element includes an actual operation amount-detection element 12, and the electrical servo-driving unit 9 is controlled by an electric control apparatus 22 based on the detected operation amount. Furthermore, the control element 11, the target operation amount-detection element 7, the actual operation amount-detection element 12, and the servo-driving unit 19 are arranged in a throttle valve casing 24. Moreover, the control element 11 is connected to the transmission member 4 with a connection spring 13 so as to be pressed toward a stopper 14 attached to the transmission member 4.
Generally, when a motor receives voltage, and begins to rotate, voltage in the direction reverse to that of the received voltage is generated in the motor, due to the generation effect of the motor. This generated voltage is called a counter voltage, and is proportional to the rotational speed of the motor. Since the motor used in an electric throttle-control apparatus is controlled to rotate to the target rotational position, when the rotation approaches the target rotational position, voltage in the direction reverse to that of the rotation of the motor is applied to the motor due to the deceleration. Thus, the counter voltage is superimposed on the fed voltage, which in turn may cause an over-current flow in the motor.
In a conventional motor, the resistance of the motor is adequately set such that an over-current due to the counter voltage does not flow in the motor. Thus, the amount of current flowing in the motor and the motor-drive circuit is suppressed below a permissible level of current for the elements in the motor-drive circuit.
However, in controlling the throttle-valve position with a motor, the throttle-valve position becomes less than stable due to small fluctuations in the torque generated within the motor, these in turn appearing as fluctuations in the rotational speed of the engine. These fluctuations of the rotational speed are not only visually perceived as fluctuations of the needle on the speed meter, but are also audibly perceived. Particularly, fluctuations in idling has been a great problem.
Since the design specification regarding the deviation in torque of a motor has been prescribed by the deviation in the average torque of the motor, it has been difficult to sufficiently suppress the fluctuation of the engine rotational speed even if the motor satisfies the design specification.
This problem has been handled by implementing proper control-characteristics of an engine-control unit whose control parameters are optimally set by a parameter survey method.
However, in its execution, since it is necessary to determine an optimal control parameter set for each electronic throttle-control apparatus in which a different motor is used, this parameter survey method is not flexible.
The present invention has been achieved with consideration to the above problems, and is aimed at providing an electric throttle-control apparatus which can suppress the fluctuations of the engine rotational speed to below a small level, and especially the fluctuations in idling, by decreasing the change in the torque generated between slots of the motor used in the electric throttle-control apparatus without adjusting a control parameter set of the engine control unit. More specifically speaking, the present invention is aimed at providing a motor such that the fluctuations of the rotational speed can be suppressed to below the level of 3% (15 rpm), which cannot be visually and audibly perceived, assuming that the idling rotational-speed is 500 rpm.
As a result of the inventors"" searching and analyzing malfunctions in electric throttle-control apparatuses, it has been found that employing the average torque of a motor to suppress torque fluctuation of the motor is not adequate, and clarification of the motor""s behavior during the brush""s transition between slots is important. That is, it has been noticed that the torque fluctuations caused during the brush""s transition between slots must be suppressed to improve responses of a motor for demands of Small Step-changes in torque.
The present invention provides the following apparatuses, motors, and internal combustion engines used in an electric throttle-control, which can improve responses of a motor for demands of Small Step-changes in torque.
To achieve the above objective, the present invention provides a first electric throttle-control apparatus, which includes a motor, a speed-reduction mechanism for reducing rotational speed of the motor, and a throttle valve connected to the speed-reduction mechanism, for controlling an open position of the throttle valve by driving the motor, wherein the motor includes a commutator with a plurality of slots, and brushes; and the number of the slots in the commutator and the arrangement of brushes on the slots are set so that even and odd number slot states appear alternately in an electrical equivalent-circuit of a wire-connection among slots including the brushes while the motor rotates.
Further, the present invention provides a second electric throttle-control apparatus such that, in the above first electric throttle-control apparatus, the number of the slots of the commutator is one of odd numbers 9, 11, and 13; the number of the brushes is 2; and the brushes are arranged in a 180xc2x0 opposed placement.
Furthermore, the present invention provides a third electric throttle-control apparatus such that, in the second electric throttle-control apparatus, the number of the slots of the commutator is one of odd numbers 9 and 11.
Moreover, the present invention provides a fourth electric throttle-control apparatus such that, in the first electric throttle-control apparatus, the number of the slots of the commutator is one of even numbers 10 and 12; the number of the brushes is 2; and the brushes are arranged by shifting their positions from a 180xc2x0 opposed placement.
Also, the present invention provides a fifth electric throttle-control apparatus such that, in the fourth electric throttle-control apparatus, the brushes are arranged in a (180-360/2n)xc2x0 non-opposed placement, where n is the number of the slots of the commutator.
In addition, the present invention provides a sixth electric throttle-control apparatus such that, in the fifth electric throttle-control apparatus, brush holders for holding the respective slots are arranged in a 180xc2x0 opposed placement.
Also, the present invention provides a seventh electric throttle-control apparatus such that, in one of the first, second, and fourth electric throttle-control apparatuses, representing the width of each brush and the peripheral pitch between slots with symbols b and c, respectively, the ratio b/c is set to a value equal to or less than 1.
Further, the present invention provides an eighth electric throttle-control apparatus, which includes a motor, a speed-reduction mechanism for reducing rotational speed of the motor, and a throttle valve connected to the speed-reduction mechanism, for controlling an open position of the throttle valve by driving the motor, wherein the motor includes a commutator with a plurality of slots, and two brushes; and a relative variation of engine rotational-speed is suppressed to within 3% by setting the number of the slots to one of odd numbers 9, 11, and 13, and arranging the two brushes in a 180xc2x0 opposed placement.
Furthermore, the present invention provides a ninth electric throttle-control apparatus, which includes a motor, a speed-reduction mechanism for reducing rotational speed of the motor, and a throttle valve connected to the speed-reduction mechanism, for controlling an open position of the throttle valve by driving the motor, wherein the motor includes a commutator with a plurality of slots, and two brushes; and a relative variation of engine rotational-speed is suppressed to within 3% by setting the number of the slots to one of even numbers 10 and 12, and arranging the two brushes in a non-opposed placement shifted from a 180xc2x0 opposed placement.
Moreover, the present invention provides a first motor used for an electric throttle-control apparatus, including a commutator with a plurality of slots, and two brushes, wherein a relative variation of engine rotational-speed is suppressed to within 3% by setting the number of the slots to one of odd numbers 9, 11, and 13, and arranging the two brushes in a 180xc2x0 opposed placement.
Further, the present invention provides a second motor such that, in the first motor, the number of the slots is one of odd numbers 9 and 11.
Also, the present invention provides a third motor used for an electric throttle-control apparatus, including a commutator with a plurality of slots, and two brushes, wherein a relative variation of engine rotational-speed is suppressed to within 3% by setting the number of the slots to one of even numbers 10 and 12; and the two brushes are arranged in a non-opposed placement shifted from a 180xc2x0 opposed placement.
Further, the present invention provides a first internal combustion engine using one of the first, second, fourth, eighth, and ninth, and electric throttle-control apparatuses.
Furthermore, the present invention provides a second internal combustion engine including an electric throttle-control apparatus in which one of the first, second, and third motors is used.